A seat belt system for restraining a vehicle occupant typically includes seat belt webbing, a seat belt locking tongue on the webbing, and a seat belt buckle. The tongue on the webbing is inserted through an opening in the buckle when the webbing has been placed about a vehicle occupant. A latch mechanism in the buckle interlocks with the tongue to secure the webbing about the occupant. When the tongue is not inserted into the buckle, foreign matter may pass through the opening into the buckle.